Transformers

ABSTRACT

The invention relates to transformer bobbins which are moulded from plastics material. The moulding provides spool portions for the primary and secondary windings of the transformer which are separated by a radially extending flange. A shroud is provided in the form of a casing which at least partially encloses the windings and has an internally formed ridge which engages the edge of the flange in an interleaving manner to minimise the &#39;&#39;tracking&#39;&#39; of current between the windings.

United States Patent @191 Miles 1 1 Sept. 30, 1975 [5 TRANSFORMERS 3.689.862 9/1972 Hilgers 336/198 X 3.750.073 7 1973 k; 33 [75) Inventor: Terence Neville Miles, Leicester, 0 m0 6/198 E l d FOREIGN PATENTS OR APPLICATIONS h I 2.103.112 8/1971 Germany 336/198 [73 I Amgncc' g g i'fj 1.263.349 5/1961 France 336/198 [22] Filed: May 21, 1974 Primary E \aminerThomas J. Kozma Appl. No: 471,980

[30] Foreign Ap plicati0n Priority Data May 23, 1973 United Kingdom 24745/73 [52] US. Cl. 336/192; 336/208; 336/209 [51] lnt. Cl. HOlF 15/10; H01F 27/30 [58] I Field of Search 336/196, 198, 208, 209, 336/192; 310/194 [56] References Cited UNITED STATES PATENTS 1.614309 l/1927 Gaucear ..'1 336/208 X Attorney, Agent, or FirmDarby & Darby [57] ABSTRACT The invention relates to transformer bobbins which are moulded from plastics material. The moulding provides spool portions for the primary and secondary windings of the transformer which are separated by a radially extending flange. A shroud is provided in the form of a casing which at least partially encloses the windings and has an internally formed ridge which engages the edge of the flange in an interleaving manner to minimise the tracking of current between the windings.

6 Claims, 4 Drawing Figures US. Patent Sept. 30,1975 Sheet10f2 3,909,761

US. Patent Sept. 30,1975 Sheet 2 of2 3,909,761

TRANSFORMERS BACKGROUND or THE INVENTION This invention is concerned with improvements in or relating to transformers, particularly to transformer bobbin assemblies to support the primaryand secondary windings thereof. 7

It has been customary to provide transformer bobbins in plastics material in units each designed to ac commodate one winding, either aprimary or a secondary winding, and to couple two such bobbin units by means of a spaced connecting member so as to leave the required distance betweenthe primary and secondary windings. Shroud members are also made to enclose the windings and minimise tracking between the transformer core and the windingsfSu ch bobbins are intricate to manufacture and require a plurality'of sepa-' rate mouldings. Moreover there are basic requirements laid down regarding creepage distances, insulation etc.

BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to provide a transformer bobbin which comprises relatively few parts in its construction and which provides a satisfactory electrical performance.

The invention provides, broadly speaking, a transformer bobbin assembly of moulded plastics material comprising a body member having two axially arranged spool portions divided by a radially extending flange, the periphery of which comprises a first interengaging portion, and a shroud means adapted at least partially to enclose the spool portions of the body member, said shroud portion being also provided with projecting means adapted to co-operate with the periphery of the flange and providing a second interengaging portion, the construction being such that at least one of said interchanging portions comprises a multiple lip, marginal portions of the other interengaging portion being adapted to interleave with said multiple lip.

Conveniently the shroud portion comprises two parts which co-operate along edges thereof adapted to lie parallel to the axis of the spool. The shroud portion may be placed in position on the body portion of the bobbin assembly by means of side flanges which received in recesses in the body portion, particularly in recesses provided in outer end portions thereof. These end portions may also be arranged to support terminal tags.

BRIEF DESCRIPTION OF THE DRAWINGS There will now be given, with reference to the accompanying drawings, a detailed description of one bobbin assembly according to the invention. It will be understood that the description is given by way of example only and not by way of limitation of the invention.

In the drawings:

FIG. 1 shows a front view of a bobbin assembly according to the invention, with one part of a shroud portion thereof in position ready for assembly;

FIG. 2 shows a side view of the body portion of the bobbin assembly with a portion of one shroud portion shown as a fragmentary view;

FIG. 3 is a perspective view of the body portion of the bobbin assembly;

FIG. 4 is a view of an alternative form of a shroud portion.

v DETAILED DESCRIPTION *The body member of the bobbin assembly as shown in the Figures comprises two axially arranged spool portions 2, 4, divided from each other by a radially extending flange 6 having a double lip 8 around its periphery and enclosing a groove 10. The arrangements of the bobbin is basically rectangular,'in the present example square, with radiussed edges and external corners to avoid'damage to the windings, of which the primary'winding may be supported upon the portion 2, and the secondary on the portion' 4, 'or'vice versa. Outer end portions 12 of the body portion define the outer limit of the windings and are provided with tenninal support means 14 adapted to receive terminal tags Iii-shown in dotted lines in FIG. 2.

It will be observed that there are provided three sets of terminal tags, two at one' side of the assembly and one at the other. It is arranged so that a choice may be made between one or other of the two sets on the one side to select which one may be more conveniently used to make the necessary electrical connection with the associated winding, according to the situation in which the bobbin is to be used.

FIGS. 1, 2 and 3 show a two-part shroud portion 20 provided to insulate the windings from the core. Each shroud portion comprises a wall portion 22 provided with two side flanges 24 arranged to be received in recesses 26 provided in the end portions 12 of the body member. These recesses are defined by ridges 28 on the end portions 12 and, by co-operation with the side flanges 24, effectively prevent any tendency to tracking. With a similar purpose, a central flange 30 provided on the inner surface of the wall portion 22 of each part of the shroud portion is received within the groove 10 of the double lip 8 on the body portion and serves to insulate the primary and secondary windings.

FIG. 4 shows an alternative form of shroud member, two of which enclose only two opposing sides of the body member. It comprises a wall portion 22, a central flange 30' and two side flanges 24.

Moulding operations to produce bobbin assemblies according to the invention are simplified, since only three mouldings are required, in contrast to four or five moulded pieces hitherto thought necessary. This economy, plus ease of handling, is achieved in addition to conforming with stringent regulations.

Various modifications may be made within the scope of the invention. For instance where it is convenient, the shroud portion may be made in one moulding which encloses the body portion of the bobbin on three sides only. Such an arrangement facilitates the escape of any heat which may build up in the transformer windings under certain circumstances of use. In any arrangement according to the invention described above, a particularly useful plastics material for the moulding of the transformer bobbin parts is glass-filled nylon.

I claim:

1. A transformer bobbin assembly comprising:

a one-piece body member formed by two axially arranged spool members having an open central portion for receiving a core of metal material and at least one radially extending intermediate first flange means dividing said body into two portions, the periphery of said first flange means forming a first interengaging portion, a second flange at each end of said body member defining a winding area between each said second flange and said first flange means,

a shroud means mounted transverse of the axis of the body member enclosing the winding areas of said body member over at least a portion of the peripheries thereof,

said shroud means having a portion projecting inwardly forming a second interengaging means cooperating with said first interengaging means,

at least one of said interengaging means comprising a multiple lip and the other of said engaging means interleaving with said multiple lip.

2. A transformer bobbin assembly as in claim 1 wherein said first interengaging means comprises a double lip having a recess and said second interengaging means of said shroud means has a portion which fits within said double lip recess.

3. A transformer assembly as in claim 1 wherein each said second flange of said body member includes third interengaging means and said shroud means includes flange members for engaging said third interengaging means.

4. A transformer assembly as in claim 1 further comprising one set of electrical terminal means on one of said second flanges and two sets of electrical terminal means on the other of said second flanges.

5. A transformer assembly as in claim 1 wherein said shro'ud means extends completely across the winding areas between said second flanges and said intermediate flange.

6. A transformer assembly as in claim 3 wherein said shroud means extends completely across the winding areas between said second flanges and said intermediate flange. 

1. A transformer bobbin assembly comprising: a one-piece body member formed by two axially arranged spool members having an open central portion for receiving a core of metal material and at least one radially extending intermediate first flange means dividing said body into two portions, the periphery of said first flange means forming a first interengaging portion, a second flange at each end of said body member defining a winding area between each said second flange and said first flange means, a shroud means mounted transverse of the axis of the body member enclosing the winding areas of said body member over at least a portion of the peripheries thereof, said shroud means having a portion projecting inwardly forming a second interengaging means cooperating with said first interengaging means, at least one of said interengaging means comprising a multiple lip and the other of said engaging means interleaving with said multiple lip.
 2. A transformer bobbin assembly as in claim 1 wherein saiD first interengaging means comprises a double lip having a recess and said second interengaging means of said shroud means has a portion which fits within said double lip recess.
 3. A transformer assembly as in claim 1 wherein each said second flange of said body member includes third interengaging means and said shroud means includes flange members for engaging said third interengaging means.
 4. A transformer assembly as in claim 1 further comprising one set of electrical terminal means on one of said second flanges and two sets of electrical terminal means on the other of said second flanges.
 5. A transformer assembly as in claim 1 wherein said shroud means extends completely across the winding areas between said second flanges and said intermediate flange.
 6. A transformer assembly as in claim 3 wherein said shroud means extends completely across the winding areas between said second flanges and said intermediate flange. 